U.S. Pat. Nos. 4,459,540; 4,634,950; 5,237,255 and 5,243,268 of Frederick W. Klatt disclosed the “Electric Rotating Apparatus and Electric Machine” system, which potentially realized the only embodiment of a brushless Wound-Rotor [Synchronous] Doubly-Fed or Singly-fed Electric Machine entity. The “Electric Rotating Apparatus and Electric Machine” system is not commercially available because many years of continued research, development, and prototyping solely by Klatt have shown new inventions are crucial for practical control and reliable operation.
Since the Klatt patents, Klatt has defined several new terms to better describe the principles of operation for the Electric Rotating Apparatus and Electric Machine, such as electro-magnetic self-commutation or rotor excitation generation. Unlike “electro-mechanical” self-commutation, “electro-magnetic” self-commutation as described in the Klatt patents uses a separate modulator and demodulator, respectively, on each side of a High Frequency Rotating Transformer (HFRT). The electromagnetic process of the HFRT directs the flow of current through the winding sets of the HFRT in accordance with the position and speed of the rotating shaft, which are available as speed-synchronized excitation for the rotor active winding sets of the PGM. If practical control was available, the resolution of control would be significantly better than electromechanical self-commutation and power is propagated without mechanical contact (i.e., brushless).
Although electromagnetic self-commutation in the embodiment of a force generating wound-rotor doubly-fed electric machine is inventive, the Klatt patents incorporated traditional phase, amplitude, and frequency modulation techniques, which were known at the time to be viable common mode modulation techniques for adjustable speed drives. Also considered was the traditional technique of synchronous modulation followed by synchronous demodulation, which are used in today's high frequency, for direct AC-to-AC multiphase conversion with a single node intermediate stage. Only after years of research, Klatt learned these traditional common mode and synchronous modulation techniques were not compatible with practical operation of the Klatt patents that incorporates an intermediate HFRT stage with multiply shared nodes. For instance, Klatt did not entirely understand the initial setup and control of the magnetizing current in the shared phases of an HFRT nor did Klatt understand the modulation techniques for energy packet transfer between the shared nodes or phases. In addition, Klatt did not understand the peculiar environmental stress placed on the electrical and electronic equipment of the Klatt patents because the Klatt patents disclose the only electric machine that closely couples high frequency electrical, magnetic, and electronic components to the moving shaft of the electric machine being controlled, which directly expose components to the harsh environment of the electric machine installation. Consequently, the Klatt patents did not disclose the new art of compensated modulation for setup, control, and sharing magnetic energy with the environmental stress requirements for the sensitive electrical and electronic equipment, which would be essential for practical control of the electric machine found in the Klatt patents.